67 lines
2.0 KiB
Python
67 lines
2.0 KiB
Python
import time
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class Ratelimiter:
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def __init__(self, allowance, period=1, operation_cost=1, mode='sleep'):
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'''
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allowance:
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Our spending balance per `period` seconds.
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period:
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The number of seconds over which we can perform `allowance` operations.
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operation_cost:
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The default amount to remove from our balance after each operation.
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Pass a `cost` parameter to `self.limit` to use a nondefault value.
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mode:
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'sleep':
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If we do not have the balance for an operation, sleep until we do.
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Return True every time.
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'reject':
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If we do not have the balance for an operation, return False.
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The cost is not subtracted, so hopefully we have enough next time.
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'''
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if mode not in ('sleep', 'reject'):
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raise ValueError('Invalid mode %s' % repr(mode))
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self.allowance = allowance
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self.period = period
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self.operation_cost = operation_cost
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self.mode = mode
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self.last_operation = time.time()
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self.balance = 0
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@property
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def gain_rate(self):
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return self.allowance / self.period
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def limit(self, cost=None):
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'''
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See the main class docstring for info about cost and mode behavior.
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'''
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if cost is None:
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cost = self.operation_cost
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time_diff = time.time() - self.last_operation
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self.balance += time_diff * self.gain_rate
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self.balance = min(self.balance, self.allowance)
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if self.balance >= cost:
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self.balance -= cost
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succesful = True
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else:
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if self.mode == 'reject':
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succesful = False
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else:
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deficit = cost - self.balance
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time_needed = deficit / self.gain_rate
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time.sleep(time_needed)
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self.balance = 0
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succesful = True
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self.last_operation = time.time()
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return succesful
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